Sailors aboard the U.S. Navy's guided-missile destroyer Porter look at damage after the ship collided early Aug. 12 in the Persian Gulf with the Japanese-owned bulk oil tanker M/V Otowasan. (MC3 Jonathan Sunderman / U.S. Navy)

The U.S. Navy destroyer Porter and a Japanese-owned tanker collided near the Strait of Hormuz at 1 a.m. Aug. 12, an impact that tore open the destroyer’s starboard side but left both crews unharmed, the U.S. 5th Fleet said in a news release.

The collision between Porter and the bulk oil tanker Otowasan, operating under a Panamanian flag, was not “combat related,” 5th Fleet said.

The circumstances of the collision — whether the collision was in the channel, the relative speeds at impact, or which ship had right of way — remain unclear.

Porter had just completed an inbound transit through the Strait of Hormuz into the Persian Gulf, said 5th Fleet spokesman Lt. Greg Raelson.

“The Japanese tanker was heading out of the [Persian] Gulf into the Strait of Hormuz” toward the Gulf of Oman, said Raelson, who added he didn’t have the exact coordinates of the collision available.

“We’re just happy that neither ship sustained any injuries or casualties,” Raelson said.

Navy photos show substantial damage to the Norfolk, Va.-based destroyer.

In one, sailors in helmets with headlamps are seen inside the gaping hole, which appears to be on the maindeck not far from the entrance to the combat information center on the starboard side. Raelson said the damages were starboard side, above the waterline.

Photos of the incident were taken by the dock landing ship Gunston Hall, which made the transit with Porter and rendered assistance afterward, Raelson said. After the collision, the ship headed into port for an assessment and repairs.

“Porter pulled into Jebel Ali in [the United Arab Emirates],” Raelson said. “They’re pier-side now and getting a status for the damages.”

This is the fleet’s second collision in four months. In May, amphibious assault ship Essex collided with the oiler Yukon while headed to San Diego for an overhaul. In that case, Essex’s commanding officer was relieved a month later, following an investigation.

Raelson said the Porter collision is under investigation and couldn’t comment on whether disciplinary action would be taken against Porter’s CO or crew.